1. Field of the Invention
The present invention relates to a data transmitting apparatus, a method thereof, a recording apparatus, and a recording and reproducing apparatus
2. Description of the Related Art
Recently, MPEG2 (Moving Picture Experts Group 2) has been used as the mainstream of video data compression-encoding methods. According to MPEG2, each field or each frame of interlaced video data is encoded corresponding to DCT (Discrete Cosine Transform). In addition, between fields or between frames, a motion compensation predictive encoding process is performed.
Video data that has been compression-encoded is recorded to for example a magnetic tape. The video data are recorded as helical tracks on the magnetic tape by a rotating head that is rotated at a predetermined speed. One frame of video data is recorded on a plurality of successive tracks. Two fields that compose one frame are dispersed on the plurality of tracks. In other words, the fields are interleaved. Video data is reproduced from the plurality of tracks at a time. Thus, dispersed fields of each frame are restored.
Now, the case of which video data that has been compression-encoded corresponding to MPEG2 and recorded on a particular record medium is reproduced and transmitted to an external device will be described. Conventionally, video data that has been compression-encoded corresponding to MPEG2 is temporarily decoded to the original video data. The original video data is transmitted to an external device. The external device performs an editing process for the received video data, performs a compression-encoding process for the edited video data, and records the encoded data to a predetermined record medium.
When video data that has been compression-encoded is temporarily decoded, transmitted, compression-encoded, and then recorded, the picture quality of video data deteriorates as the signal deteriorates. In addition, to transmit the decoded video data, the frequency band of the transmission path should be widened. Thus, there are needs to transmit video data that has been compression-encoded.
Conventionally, as with a VCR (Video Cassette Recorder), when a reverse reproducing operation of which video data that has been compression-encoded is reproduced in the reverse direction on the time axis of the recording operation is performed, a frame memory for changing the display order of fields is used. In other words, decoded video data is stored in the frame memory. The first field (the top field on the time axis) and the second field (the bottom field on the time axis) are read in the reverse order. Thus, when the reverse reproducing operation is performed, video data is smoothly and naturally displayed.
On the other hand, when video data that has been compression-encoded is reversely reproduced, transmitted to an external device, decoded by the external device, and then displayed on a monitor, it is necessary to inform the external device that the video data has been reversely reproduced. This is because the external device cannot determine whether the video data has been reversely reproduced.
In other words, as described above, video data that has been compression-encoded is field-interleaved and recorded frame by frame to a magnetic tape. When video data is reversely reproduced, the order of frames is different from the recording operation. However, the order of fields is the same as the recording operation. Consequently, since fields are reproduced in the different direction from frames, the resultant picture is unnaturally displayed.
Thus, when video data that has been compression-encoded corresponding to MPEG2 and recorded on a record medium is reversely reproduced, transmitted to an external device through a transmission path, and then decoded and reproduced by the external device, it should be informed that the video data has been reversely reproduced.
In particular, if video data that has been compression-encoded contains forwardly reproduced data and reversely reproduced data, information that represents the relation between frames and forward/reverse reproducing operations is required. Otherwise, the display order of the top field and bottom field of received video data cannot be changed with the frame memory on real time basis.
An object of the present invention is to provide a data transmitting apparatus, a method thereof, a recording apparatus, and a recording and reproducing apparatus that allow video data that has been compression-encoded and reversely reproduced to be naturally reproduced in the reverse direction.
A first aspect of the present invention is a data transmitting apparatus for transmitting video data that has been compression-encoded, comprising a record medium on which the video data has been recorded, a reproducing means for reading the video data from the record medium in the different direction on the time axis from the video data that has been recorded, and a transmitting means for generating information that represents that the video data has been read from the record medium in the different direction when the video data is read from the record medium by the reproducing means in the different direction, placing the generated information to a data stream of the video data, and transmitting the resultant data stream.
A second aspect of the present invention is a recording apparatus for recording video data that has been compression-encoded to a record medium, comprising a receiving means for receiving a data stream of the video data, an inverting means for inverting a flag that represents the display order of fields of the video data, the flag being placed in the data stream, and a recoding means for recoding the data stream with the inverted flag to the record medium.
A third aspect of the present invention is a recording and reproducing apparatus for recording video data that has been compression-encoded to a record medium and reproducing that video data from the record medium, comprising a recording means for recording the video data to the record medium, a reproducing means for reproducing the video data from the record medium in the different direction on the time axis from the video data that has been recorded, and a transmitting means for generating information that represents that the video data has been read from the record medium in the different direction when the video data is read from the record medium by the reproducing means in the different direction, placing the generated information to a data stream of the video data, and transmitting the resultant data stream.
A fourth aspect of the present invention is a data transmitting method for transmitting video data that has been compression-encoded, comprising the steps of (a) recording the video data to a record medium, (b) reproducing the video data from the record medium in the different direction on the time axis from the video data that has been recorded, and (c) generating information that represents that the video data has been read from the record medium in the different direction when the video data is read from the record medium at step (b) in the different direction, placing the generated information to a data stream of the video data, and transmitting the resultant data stream.